Expansible-chamber and positivedisplacement type pump of variable capacity



March 23, 1954 W|DMER 2,672,819

EXFANSIBLE-CHAMBER AND POSITIVE-DISPLACEMENT TYPE PUMP OF VARIABLE CAPACITY Filed Dec. 1, 1949 3 24 provided thereon. For the purpose of axially displacing the drum 25, the latter on its circumference carries a crown gear 25 with which a worm 21 meshes which is rotatably mounted in the inner casing 4.

The pump, in the position shown of the adjusting drum 25, operates so that when shaft I8 rotates, the large-diameter piston 8 suck liquid through the ports 13, and the small-diameter pistons 8a suck through the ports [3a, and all the pistons deliver liquid through the pressure valves [4 into the pressure. chamber 28 which through a pipe 29 may be connected to any prime mover. The effective stroke of the large-diameter pistons 8 then equals the distance s1 in that the piston end-faces I 2 on over-running the control edges l5 cannot force liquid back into the space la. The delivery stroke of the small-diameter pistons 8a, however, equals the entire piston stroke s. When drum is displaced to the left, the delivery stroke s1 of the large-diameter pistons 8 decreases, while that of the small-diameter pistons 8a remains constant, since the latter suck through the valves and not through the control ports l3a. When such displacement of drum. 25 is only slightly greater than the distance s1, which is the maximum effective delivery stroke of the large-diameter pistons, then the delivery of the latter is reduced to zero, while the small-diameter pistons still deliver the same quantity as in the position for maximum delivery. Only when the drum 25 is still further displaced to the left, the small-diameter pistons also will deliver less'when they in their outer deadcenter position uncover the ports I 3a so that part of the liquid sucked into the cylinders is returned through the ports l3a into space la. The "position of the control ports I 3, I311 in accordance with the form of invention shown in Figs. 1 and 3, for the sake of clarity is also shown in Fig. 6

which illustrates a developed cylindrical section through all the piston axes. In'Fig; 6, the otfset of the said ports is readily visible.

The advantage of the pump shown is that, in the case of pumps for which at low pressure a maximum delivery and'at high pressure a minimum delivery is required, a very great delivery can be attained at low pressure by means of all the pistons, while at high pressure the largediameter pistons may be entirely out out so that the latter no longer load the wabbler plate 10 and thus the ball bearings l6 and 23 which therefore, have to be fitted only to the pressure of the small-diameter pistons.

In the form shown in Fig. 2, the adjusting" drum 30 is not threadedly engaged, but supported through a spring 3| which in turn abuts against a cover 32 fixed to the casing 4. When the discharge pressure rises, the drum 30 is pushed upwardly through the liquid" pressure acting onto the pistons, against the pressure of spring 3|, so as to automatically reduce the delivery.

Instead of providing alternate largeand smallborecylinderslin the case of twelve cylinders,

e. g. six largeand six small-borepylinders);

there may be disposed nine large-bore cylinders T and only three small-bore'cylinders Ia at a uniform spacing, as'shown in Fig. 4. In similar manner, eight large-bore and four small-bore cylinders may be provided, as shown in Fig. 5 for example. I

the case of the disposition shown in Fig. 4, for a group of one small and three larg pistons.

Instead of incorporating pistons of two sizes, there may be provided threegroups of pistons 7, la, lb of different diameters, and the control ports 13, l3a, l3b may be staggered, as shown in development in Fig. 8. In such arrangement also, the delivery decreases when the drum 25 is displaced to the left, and the ratio between maximum and minimum delivery may be made very great. In such arrangement, there may be provided, e. g. in a twelve-cylinder pump, four large, four intermediate, and four small pistons.

In the form of invention shown in Fig. l, the large-bore cylinders may be equipped at 3'! with a suction valve 35, similarly as the small-bore cylinders Ta. Such provision permits to still further increase the delivery, in the outer-most position of the adjustment drum toward the cylinders, since in such position liquid no longer may flow through the control ports l3 back into space la when the said ports are displaced somewhat toward the left.

In the small-bore cylinders la, the control ports l3a may be omitted, provided that the liquid delivered at high pressure always will be consumed by the prime movers or will be thrown off through a safety valve which is set for this high pressure.

The ports l3a in the small-bore cylinders Ia of Fig. 1 may be disposed somewhat farther to .the right so as to be uncovered by the pistons 811 be fore the large-diameter pistons 8 entirely cease to deliver.

It further will be readily appreciated by anyone skilled in the art that the position of the control ports depends on the position of th piston, end-face l2 at dead-centers. If, therefore, one group of pistons are made shorter, the position of the control ports in the respective cylinders has to be correspondingly changed, 1. e. in the case of shorter pistons the said ports have to be placed further to the left.

What I claim as new and desire to secure by Letters Patent, is:

l. A pump comprising a stationary cylinder block provided with at least two groups of parallel pump cylinder bores, a plurality of pump plungers'respectively reciprocable in said cylinder bores and having the outer ends thereof extend ing to the exterior of said cylinder block, a rotatably mounted Wobbler plate coacting with the outer ends of'said pump plungers exter-iorly of said cylinder block, said Wobbler-plate being mounted for slidable displacement in the direction of the axes of said pump plungers, adjusting means operatively associated with said Wobblerplate and operable slidably to displace said Wobbler plate in the direction of the axes of said pump plungers towards and away from said cylinder block, resilient means biasing said pump plungers into operative engagement with the wobbler plate in all positions of slidable displacement of the plate, each of said pump cylinderbores having inlet and outlet control ports, the cylinder boresof one of said groups. of bores having a control port laterally opening into the respective bore, said last-named control port being spaced in the direction toward said Wobblerplate from inner dead center position of the inner plunger end when said wobbler plate is at its In Fig. 7, the arrangement of the control'port's' I I 3, I 311 of the largeand small-bore cylinders-'1' and M respectively, is shown in development for innermost position with respect to the cylinder block, the distance between saidlast-named consmaller than the axial length of the Wobbler plate displacement path, whereby when the Wobbler plate is axially moved outwardly from its innermost position through an extent greater than said distance, said last-named control port remains uncovered during the pressure stroke, and at inner dead center position of the plunger, to prevent any delivery .by the group of cylinder bores provided with said control port, while the other group of cylinder bores continues to deliver.

2. A pump as set out in claim 1, in which said one group of cylinder bores are of larger diameter than the remaining cylinders.

3. A pump as set out in claim 1, in which two such groups of cylinders are provided, the pistons of one group ceasing earlier to deliver than the pistons of the other group as the Wobbler-plate is slidably moved away from the cylinders.

4. A pump as set out in claim 1, in which the said control port of each of said one group of d cylinder bores constitutes the sole inlet port to the respective cylinder bore.

5. A pump as set out in claim 1, in which the said control port of each of said one group of cylinder bores constitutes an inlet port to the respective cylinder bore, and wherein each of said one group of cylinder bores also includes a valved inlet port spaced from the said control port in the direction opposite said Wobbler-plate.

6. A pump as set out in claim 1, in'which the said other group of cylinders only each include a valved inlet port adjacent the end thereof opposite said Wobbler-plate.

7. A pump as set out in claim 1, in which an even number of cylinders are provided, said one group of cylinders comprising one half of all the cylinders and being provided with bores of greater diameter than the remaining cylinders, with the large-bore and small-bore cylinders alternating in annular arrangement about the pump axis.

8. A pump comprising a stationary cylinder block provided with two groups of parallel pump cylinder bores, said bores of one group having a relatively large diameter, and said bores of the other group having a relatively small diameter,

pump plungers reciprocable in said bores and having the outer ends thereof extending to the exterior of said cylinder block, said plungers having a diameter corresponding to that of the respective bores, a rotatably mounted Wobbler plate coacting with the outer ends of said pump plungers exteriorly of said cylinder block, said Wobbler-plate being mounted for slidable displacement in the direction of the axes of said pump plungers, adjusting means operatively associated with said Wobbler-plate and operable slidably to displace said Wobbler plate in the direction of the axes of said pump plungers toward and away from said cylinder block, resilient means biasing said pump plungers into operative engagement with the Wobbler plate in all positions of slidable displacement of the plate, each of said pump cylinders having inlet and outlet control ports, the cylinder bores of said group of relatively large bores having a control port opening laterally into the respective bores, each of said last-named control ports being spaced in the direction opposite said Wobbler-plate from the inner dead center position of the plunger inner end face when said Wobbler plate is at its extreme position remote from the cylinder block, the distance between each of said last-named control ports and said inner dead center position of the corresponding plunger inner end face being smaller than the axial length of the Wobbler plate displacement path, whereby when the Wobbler plate is slidably moved away from the cylinder block through an extent greater than said distance, said last-named control ports of the cylinder bores of larger diameter remain uncovered during the pressure stroke and at the inner dead center position of the plunger to prevent any delivery by the group of cylinder bores of larger diameter, while the group of cylinder bores of smaller diameter continue to deliver.

9. A pump as set out in claim 8, comprising twelve cylinders of which eight are of large bore and four of small bore.

10. A pump as set out in claim 8, comprising twelve cylinders of which nine have large bores and three small bores, the latter being annularly disposed atequal distances from each other about the pump axis.

LEO PETER WIDMER.

References Cited in the flle of this patent UNITED STATES PATENTS Number Name Date 2,114,565 Kovach Apr. 19, 1938 2,193,612 Alden Mar. 12, 1940 2,439,879 Allen Apr. 20, 1948 2,534,153 Widmer Dec. 12, 1950 2,578,139 Jones Dec. 11, 1951 2,578,146 Newton Dec. 11, 1951 FOREIGN PATENTS Number Country Date 316,885 Germany 1919 867,082 France 1941 

